1. Field of the Invention
This invention relates to an image forming apparatus including a copying apparatus or the like, more particularly to apparatus for controlling the switching of a power supply to the apparatus to promote an image forming process.
2. Description of the Prior Art
In addition to a copy start switch, a conventional copying apparatus has in general a main switch for supplying power to the electric loads within the machine for achieving such a processing as a charging or an exposing and the control unit which is provided to achieve a timing control for the loads. Various electric loads are normally activated by the main switch to operate a cooling fan or set a copying apparatus in a ready condition of "copy start."
However, those electric loads are frequently deenergized automatically after completion of copying in order to prevent noise caused by the fan or to save power. The main switch is therefore so constructed to be activated only by a manual driving of a switch actuator and thereafter a relay holds a power line which is shut off by releasing the relay after the completion of copying.
The turning on or off of the power line is frequently accomplished or checked by an operator taking into consideration a position of the handle of the main switch. The operator would therefore be unsure of the condition of the machine if the acutator position is not definitely preset. Meanwhile, an additional mounting of a "manual off" switch for releasing a relay manually would make the apparatus construction complex. The conventional apparatus had thereon an exclusive safety circuit or a protection circuit to prevent the occurrence of a malfunction in the apparatus and suppress the overcurrent on the AC line.